changes:
*no more lags in ui, swiping is buttery smooth
*new notification panel
*new xperia keyboard animation while typing
*new apps like play memories mobile, sony select, sony explore, file commander
*developer option can now be diactivate
*battery in settings changed to power management now with extended standby mode option
*better gaming performance, almost no more lags
*no more top contacts widget
*little change in looks of google search/voice in homescreen, now no more underline/lines
*some apps removed like power saver, astrofile manager
*when you go to keyboard settings while using keyboard, going back to keyboard will took about 5 secs unlike in ics going back will only took 1 sec

so far those are the changes i experience.for my conclusion the jb update is worth it in terms of performance:-)

it hangs a little while receiving a call......may be it's due to heat....at the weather at that moment was so hot and I was putting it in a silk case....
but about the phone it's perfect good
also about it's battery it dropped 40% in just 6 hours.....I think it might be a problem too unless these kind of phone have a low lasting battery already :D

humming mob, 23 Mar 2013pls dont compare music quality of sony mobile with samsung mobile.The default headset is not u... morehey buddy do u tell me the sound quality of the headset u have mention SONYMH750. Actually I have also got Xperia J and I am not satisfying with the headset I have got out of the box.

nishar2, 24 Mar 2013Its not Mini Sim....
Its regular one......
nisar-funIts Mini SIM. A regular SIM card is the size of a creditcard, and thankfully not used anymore, but most SIM cards still come in a creditcard size SIM adapter.

Hi guys please guide us those who r serious and using this phone.Does this phone have any problem like hanging or picture problem?I am going to buy J or L. where L has very limited phone memory.so guide me which one is best for me i require front camera and minimum 1gb memory user define.

Guys if u r serious so telling us those who are using this Xperia j.is there any hanging? which phone is best xperia j or xperia L.where xperia L has mini phone storage. plz tell seriously. i m goning 2 buy either J or L.

vinu, 23 Mar 2013plzzz plzzzz dont purchs this ph it is totaly useles and money wast ph becus its height is sma... morepls dont compare music quality of sony mobile with samsung mobile.The default headset is not upto the mark, that is true. but u can change the headphone, then sound is good.currently i m using with sonyMH750 head phone. the other thing u mention that is corrrect. camera is only like 3.2mp.& also hav little lag.